The invention concerns a device for moving a pig through a conduit, such as pipeline, comprising at least one pulling element having at least one sealing means, and a sealing means for such a device.
Conventional devices of this kind are used e.g. for cleaning or checking for leaks in conduits, such as pipelines, wherein the pulling element, is suitable for receiving a cleaning or a measuring means by providing the generally cylindrical pulling element with such a means or by coupling such means to the pulling element to be pulled along therewith. In order for the medium transported in the conduit to drive the pulling element the pulling element comprises, in general, at least one sealing means which abuts on the inside of the conduit and, at the same time, provides central guidance of the pulling element along the longitudinal central axis of the conduit.
The diameter of the sealing means thereby corresponds substantially to the standard width of the corresponding conduit such that several of these devices are required to control conduits of various standard widths. If a conduit comprises portions with varying cross-sections, such as widening or narrowing parts, or branches, in particular T- or Y-shaped branches, it is generally not possible to guide pigs through such conduits.
It is the underlying purpose of the present invention to further develop a device of the above mentioned kind such that a pig can be moved through conduits of varying cross-sections thereby ensuring sealing between the sealing means and the inner pipe wall.
In accordance with the invention, this object is achieved with a device of the above mentioned kind in that the sealing means comprises a supporting structure with variable circumference having at least one sealing element, disposed at the circumference of the supporting structure and made from a flexible material.
In the device in accordance with the invention, the supporting structure with variable circumference permits use of the device in conduits of various cross-sections and, in particular, in conduits whose cross-sections narrow or widen. The sealing element disposed at the circumference of the supporting structure can be deformed to ensure sealing between the sealing element and the inner pipe wall to maintain abutment on the inner pipe wall and therefore sealing within the range of cross-sectional conduit areas for which the device is to be used.
A variant of this embodiment thereby comprises several partially-cylindrical sealing sections, disposed one next to the other in the circumferential direction and communicating with each other via the lateral end regions of their outer sides, which are either individually firmly connected to one another to form the annular sealing element or form same as a single piece. The radius of the partially-cylindrical sealing sections in this embodiment, made from a flexible material, can vary in dependence on the cross-section of the conduit or on the corresponding circumference of the supporting structure, wherein the abutting or pressed-together lateral end regions of the sealing sections always guarantee good sealing.
In accordance with a further embodiment, a sealing ring is provided which is formed from a single piece and corrugated in the circumferential direction, and which can be folded in dependence on the cross-section of a conduit or of the corresponding circumference of the supporting structure to always abut against the inner pipe wall. The sealing ring can e.g. be formed such that it is not or only slightly corrugated for the largest pipe width of the device or for the largest circumference of the supporting structure, and such that it is strongly corrugated for the smallest possible circumference of the supporting structure.
The sealing element is preferably made from a polymer, in particular, polyurethane, due to its high wear resistance.
The sealing means preferably comprises a sealing diaphragm which extends from the sealing element(s) disposed at the circumference of the supporting structure, radially towards the pulling element to which it can be mounted e.g. in any arbitrary fashion. The sealing diaphragm is preferably disposed at the radially inward side of the sealing element. In a preferred embodiment, the sealing element and the sealing diaphragm are firmly connected to each other. For a one-piece sealing element in the form of a sealing ring, the sealing ring and the diaphragm can, optionally, also be formed from a single piece.
The sealing means is preferably bowl-shaped and extends in a convex fashion towards the drawing direction of the pulling element, wherein the convex shape of the sealing means increases, the narrower the conduit or the smaller the variable circumference of the supporting structure. In this case, the sealing diaphragm is also bowl-shaped and extends in a convex fashion in the same direction as the convexity of the sealing means to adapt to cross-sectional changes of a conduit.
The sealing diaphragm preferably comprises a flexible texture formed, in particular, of net-like interwoven bands, fixed e.g. via loops at the ends to the supporting structure, and can comprise e.g. axially and also radially extending bands, wherein either several partially-cylindrical sealing elements or a one-piece sealing ring is connected to the radially extending bands. The texture of sewn up bands forming the diaphragm is preferably made from a polymer, in particular a polyamide, such as nylon, perlon or the like.
The supporting structure of variable circumference advantageously comprises supporting arms which are arranged substantially radially and are pivotable about axes, extending perpendicular to the longitudinal central axis of the pulling element. The sealing element(s) is/are hinged in a pivotable fashion to the outer ends of the supporting arms. Such pivotable mounting to the supporting arms enables, in particular, passage of the inventive device through pipe bends without damaging the sealing element, while assuring that the sealing elements abut the inner pipe wall to maintain good sealing.
The supporting arms of the supporting structure are preferably biased radially outwardly via of a spring force, wherein the sealing means automatically adapts to conduits of varying cross-section. The supporting arms are biased radially outwardly by appropriate substantially equal spring forces to simultaneously guarantee central guidance of the pulling element, a cleaning means, a measuring means or other members connected to the pulling element. Such a supporting arm can e.g. be biased radially outwardly via a disk spring set.
Each supporting arm preferably comprises a roller at its outer end for guidance along the inner wall of a conduit such that the sealing element(s), mounted e.g. via pivotable receptacles disposed at the outer ends of the supporting arms, can be pressed with a predeterminable force against the inner pipe wall to reduce friction on the inner pipe wall and associated wear.
To prevent damage to a conduit and to a supporting arm, in particular in pipe bends, each supporting arm preferably comprises a supporting roller in the region of its pivot axis for support on the inner wall of the pipe, wherein, at least for pipes of small cross-section, at least some of the supporting arms can assume extreme positions substantially parallel to the longitudinal central axis of the pipe.
A further development of the inventive device provides that the supporting arms are synchronized. As a result thereof, the device is also suitable for conduits or pipelines comprising branches, (e.g. Y- or T-shaped) since, during passage of a sealing means through such branches, those radially outwardly biased supporting arms which do not experience any counter pressure from the inner pipe wall due to the branching, are held by neighboring supporting arms which abut on the inner pipe wall opposite to the branch such that the free supporting arms cannot spring out radially, thereby reliably preventing damage to the sealing element and/or the diaphragm. Preferably, each pair of neighboring supporting arms are synchronized to thereby ensure maintenance of an angle with respect to the longitudinal central axis of the pulling element, which varies between 1xc2x0 and 5xc2x0, in particular between 2xc2x0 and 3xc2x0.
The supporting arms can comprise e.g. pins extending at a separation from and parallel to their pivot axes, wherein the ends of each pair of facing pins of neighboring supporting arms protrude into a common holding means to guarantee limited relative motion of the pins, wherein the limited relative motion corresponds, in particular, to an angular difference of between 1xc2x0 and 5xc2x0 in the angles between the respective supporting arms and the longitudinal central axis of the pulling element. The holding means may e.g. be formed by clamps.
Alternatively, the supporting arms can alternately comprise one and two guiding plates at a separation from their pivot axes, wherein each of the guiding plates of a supporting arm engages between the two guiding plates of the neighboring supporting arm to thereby ensure limited relative motion. Instead of alternately providing the supporting arms with one and two guiding plates, each supporting arm can comprise, at a separation from the pivot axis, one guiding plate directed towards the one neighboring supporting arm and two guiding plates directed towards the other neighboring supporting arm, wherein the guiding plate directed towards the one neighboring supporting arm engages between the two guiding plates of the neighboring supporting arm to thereby ensure limited relative motion.
Tests have shown that it is advantageous when the supporting structure comprises twelve supporting arms to ensure good guidance of the pulling element along a conduit and good sealing of both the sealing element supported by the supporting structure and of the diaphragm, optionally provided on the sealing element(s).
In a preferred embodiment, the supporting structure is mounted to the pulling element via a central sleeve which can be fixed thereto. If the inventive sealing element comprises a sealing diaphragm, it is also preferably mounted to such a central sleeve.
To absorb transient pressure changes of the medium conveyed in the conduit, so-called shock waves, the central sleeve is fixed to the pulling element, preferably with limited axial displacement such that the inventive sealing means can axially move in response to such a shock wave, to prevent, in particular, damage to the sealing element and diaphragm. The central sleeve is preferably fixed to the pulling element in a manner axially displaceable in opposition to a spring force.
In a further preferred embodiment, the central sleeve is fixed to the pulling element in a radially pivotable fashion, in particular via a ball and socket joint. This facilitates passage through pipe bends, in particular, of devices comprising several sealing means disposed on a pulling element, in that at least some of the sealing means can be pivoted with respect to the pulling element and thereby are always disposed substantially perpendicular to the longitudinal central axis of the conduit, wherein the supporting structure of the sealing means thereby maintains a substantially circular cross-section to reduce wear of the sealing elements and maintain good sealing.
A preferred embodiment provides at least two sealing means disposed on a pulling element, at least one of which can be radially pivoted on the pulling element. In a device having a pulling element comprising two sealing means, both sealing means may be radially pivotable, or only one sealing means may be radially pivotable and the other not. In general, the inventive device comprises three or four sealing means of which e.g. the central one is disposed on the pulling element in a radially pivotable fashion and the others are stationary. The inventive device can, of course, also comprise several such sealing means, wherein in a device with e.g. five sealing means, the second and the fourth sealing means could be radially pivotable on the pulling element, whereas the first, third and fifth sealing means could be disposed in a radially fixed manner. As mentioned above, all sealing means are disposed on the pulling element in an axially displaceable manner, independent of whether or not they are pivotable.
The invention also concerns a sealing means in a device for moving a pig through a conduit, such as a pipeline, which comprises at least one of the above mentioned features.
The invention is described in more detail below with respect to preferred embodiments and with reference to the drawings.